1. Field of the Invention
The present invention generally relates to semiconductor device and, particularly, to semiconductor device having a fuse.
2. Description of Related Art
Recently, semiconductor device which have a fuse for switching functions or electric characteristics and increasing yield by defect remedy have been developed.
FIG. 5 is a plan view which schematically shows a part of the structure of a semiconductor device 10 having a fuse according to a related art. The semiconductor device 10 has a fuse 11 and a fuse opening 12. The fuse 11 is mounted inside a semiconductor chip in order to switch functions or electric characteristics and increase yield by remedying defects. The fuse 11 is electrically blown due to heating by laser application, thereby enabling the switching of circuits.
FIG. 6 is a cross-sectional view along line VI-VI of FIG. 5. The semiconductor device 10 has the fuse 11, the fuse opening 12, a semiconductor substrate 14, an interlayer insulating film 15 and an interlayer insulating film 16. The fuse 11 is formed on the lower-layer interlayer insulation film 15 which is deposited on the semiconductor substrate 14. On the fuse 11 is the second-layer interlayer insulating film 16 which is deposited so as to cover the fuse 11. Further, in order to blow the fuse 11 by laser application, the fuse opening 12 is created above the cutout portion of the fuse 11, so that the thickness of the interlayer insulating film 16 is small in that area. FIG. 7 is a circuit diagram which shows a part of the semiconductor device 10 having the fuse illustrated in FIG. 5. As shown in FIG. 7, the fuse 11 is electrically connected to a fuse determination circuit 17 through one pathway.
The multilayer structure on the recent semiconductor device 10 causes an increase in variations in the remaining film of the interlayer insulating film 16 under the fuse opening 12 above the fuse 11. If the interlayer insulating film 16 above the fuse 11 is too thin, the fuse 11 and the interlayer insulating films 15 and 16 are subject to breakdown due to electrical damages such as electrostatic discharge during manufacturing process and package assembly process, which degrades the reliability of the semiconductor device 10. In order to overcome the above drawbacks, various techniques have been proposed including those disclosed in Japanese Unexamined Patent Application Publications Nos. 2001-135792, H11-214389, H08-213469, for example.
The electrostatic discharge is likely to occur particularly at a crossing portion 13 where the fuse 11 and an edge of the fuse opening 12 cross each other because of charge concentration. As shown in FIGS. 5 and 7, one fuse 11 which crosses with the edge of the fuse opening 12 is built with a single electrical system. Thus, if electrostatic discharge occurs in this fuse 11, the fuse 11 is electrically blown, which leads to degradation in the reliability of the semiconductor device 10.
On this account, there is a growing demand for the development of a highly reliable semiconductor device with a fuse even when there are variations in a remaining film above the fuse.